1. Field of the Invention
The present invention relates to a liquid ejection apparatus, an image forming apparatus and a liquid storage amount judgment method, and more particularly, to a liquid ejection apparatus used in an inkjet type recording apparatus.
2. Description of the Related Art
In the related art, there is technology for controlling the back pressure by applying a negative pressure to the nozzle section, in order to prevent leakage of ink from the nozzles of a recording head. The following invention has been disclosed as apparatuses for controlling the back pressure of a recording head.
The invention disclosed in Japanese Patent Application Publication No. 2003-300331 comprises: an ink bag connected to a recording head, a seal device which hermetically encloses the ink bag, a suctioning device which performs suctioning to create a negative pressure in the space between the seal device and the ink bag, and a negative pressure determination device which determines the pressure of the space between the seal device and the ink bag.
The negative pressure determination device determines the state of negative pressure change in the space between the seal device and the ink bag when a negative pressure is created by the suctioning device, so that the residual amount of ink in the ink bag is determined. Then, the back pressure of the recording head is controlled on the basis of the residual amount of ink thus determined.
Furthermore, the invention described below has been disclosed as a device for determining the liquid pressure of the ink, and the remaining amount of ink, inside a recording head.
In the invention disclosed in Japanese Patent Application Publication No. 59-104947, one portion of the wall of an ink supply channel inside a recording head is constituted by a flexible film, and by determining the displacement of this flexible film, the pressure and remaining amount of the ink inside the recording head are determined.
However, although the invention disclosed in Japanese Patent Application Publication No. 2003-300331 determines the pressure in the space between a seal device and an ink bag by means of a negative pressure determination device, it does not determine the pressure of the ink inside the ink bag. Therefore, when determining the remaining amount of ink, it is necessary to halt the ejection of ink from the recording head and set the pressure of the ink inside the ink bag to a uniform pressure. Consequently, the accuracy of determining the remaining amount of ink declines when ink is being ejected from the recording head, and there is a possibility that the back pressure of the recording head cannot be controlled stably.
Moreover, in the invention disclosed in Japanese Patent Application Publication No. 59-104947, the flexible film deteriorates due to the application of repeated displacement of the flexible film. When the flexible film deteriorates, the determination accuracy of the ink pressure and the determination accuracy of the remaining amount of ink decline. In particular, in the case of a recording head which is used in a recording apparatus that consumes a large amount of ink, the amount of deformation of the flexible film and the number of deformations of the film tend to increase, and therefore, the load applied to the flexible film becomes larger and there is a possibility that deterioration will occur more rapidly.